ESTree AST Descriptor Syntax - gregswindle/eslint-plugin-crc GitHub Wiki

This document specifies the extensions to the core ESTree AST types to support the ES5, ES6 (ES2015), ES7 (ES2016), and ES8 (2017) grammars.

📖 Estree/estree. (2017, October 05). Retrieved December 01, 2017,
from https://github.com/estree/estree

ES5 / ES2009 AST node types
ES6 / ES2015 AST node types
ES7 / ES2016 node types
- BinaryOperator
- AssignmentOperator
ES8 / ES2017 AST node types
- Function
- AwaitExpression

ES5 / ES2009 AST node types

Node objects

ESTree AST nodes are represented as Node objects, which may have any prototype inheritance but which implement the following interface:

interface Node {
    type: string;
    loc: SourceLocation | null;
}

The type field is a string representing the AST variant type. Each subtype of Node is documented below with the specific string of its type field. You can use this field to determine which interface a node implements.

The loc field represents the source location information of the node. If the node contains no information about the source location, the field is null; otherwise it is an object consisting of a start position (the position of the first character of the parsed source region) and an end position (the position of the first character after the parsed source region):

interface SourceLocation {
    source: string | null;
    start: Position;
    end: Position;
}

Each Position object consists of a line number (1-indexed) and a column number (0-indexed):

interface Position {
    line: number; // >= 1
    column: number; // >= 0
}

Identifier

interface Identifier <: Expression, Pattern {
    type: "Identifier";
    name: string;
}

An identifier. Note that an identifier may be an expression or a destructuring pattern.

Literal

interface Literal <: Expression {
    type: "Literal";
    value: string | boolean | null | number | RegExp;
}

A literal token. Note that a literal can be an expression.

RegExpLiteral

interface RegExpLiteral <: Literal {
  regex: {
    pattern: string;
    flags: string;
  };
}

The regex property allows regexes to be represented in environments that don’t support certain flags such as y or u. In environments that don't support these flags value will be null as the regex can't be represented natively.

Programs

interface Program <: Node {
    type: "Program";
    body: [ Directive | Statement ];
}

A complete program source tree.

Functions

interface Function <: Node {
    id: Identifier | null;
    params: [ Pattern ];
    body: FunctionBody;
}

A function declaration or expression.

Statements

interface Statement <: Node { }

Any statement.

ExpressionStatement

interface ExpressionStatement <: Statement {
    type: "ExpressionStatement";
    expression: Expression;
}

An expression statement, i.e., a statement consisting of a single expression.

Directive

interface Directive <: Node {
    type: "ExpressionStatement";
    expression: Literal;
    directive: string;
}

A directive from the directive prologue of a script or function. The directive property is the raw string source of the directive without quotes.

BlockStatement

interface BlockStatement <: Statement {
    type: "BlockStatement";
    body: [ Statement ];
}

A block statement, i.e., a sequence of statements surrounded by braces.

FunctionBody

interface FunctionBody <: BlockStatement {
    body: [ Directive | Statement ];
}

The body of a function, which is a block statement that may begin with directives.

EmptyStatement

interface EmptyStatement <: Statement {
    type: "EmptyStatement";
}

An empty statement, i.e., a solitary semicolon.

DebuggerStatement

interface DebuggerStatement <: Statement {
    type: "DebuggerStatement";
}

A debugger statement.

WithStatement

interface WithStatement <: Statement {
    type: "WithStatement";
    object: Expression;
    body: Statement;
}

A with statement.

Control flow

ReturnStatement

interface ReturnStatement <: Statement {
    type: "ReturnStatement";
    argument: Expression | null;
}

A return statement.

LabeledStatement

interface LabeledStatement <: Statement {
    type: "LabeledStatement";
    label: Identifier;
    body: Statement;
}

A labeled statement, i.e., a statement prefixed by a break/continue label.

BreakStatement

interface BreakStatement <: Statement {
    type: "BreakStatement";
    label: Identifier | null;
}

A break statement.

ContinueStatement

interface ContinueStatement <: Statement {
    type: "ContinueStatement";
    label: Identifier | null;
}

A continue statement.

Choice

IfStatement

interface IfStatement <: Statement {
    type: "IfStatement";
    test: Expression;
    consequent: Statement;
    alternate: Statement | null;
}

An if statement.

SwitchStatement

interface SwitchStatement <: Statement {
    type: "SwitchStatement";
    discriminant: Expression;
    cases: [ SwitchCase ];
}

A switch statement.

SwitchCase

interface SwitchCase <: Node {
    type: "SwitchCase";
    test: Expression | null;
    consequent: [ Statement ];
}

A case (if test is an Expression) or default (if test === null) clause in the body of a switch statement.

Exceptions

ThrowStatement

interface ThrowStatement <: Statement {
    type: "ThrowStatement";
    argument: Expression;
}

A throw statement.

TryStatement

interface TryStatement <: Statement {
    type: "TryStatement";
    block: BlockStatement;
    handler: CatchClause | null;
    finalizer: BlockStatement | null;
}

A try statement. If handler is null then finalizer must be a BlockStatement.

CatchClause

interface CatchClause <: Node {
    type: "CatchClause";
    param: Pattern;
    body: BlockStatement;
}

A catch clause following a try block.

Loops

WhileStatement

interface WhileStatement <: Statement {
    type: "WhileStatement";
    test: Expression;
    body: Statement;
}

A while statement.

DoWhileStatement

interface DoWhileStatement <: Statement {
    type: "DoWhileStatement";
    body: Statement;
    test: Expression;
}

A do/while statement.

ForStatement

interface ForStatement <: Statement {
    type: "ForStatement";
    init: VariableDeclaration | Expression | null;
    test: Expression | null;
    update: Expression | null;
    body: Statement;
}

A for statement.

ForInStatement

interface ForInStatement <: Statement {
    type: "ForInStatement";
    left: VariableDeclaration |  Pattern;
    right: Expression;
    body: Statement;
}

A for/in statement.

Declarations

interface Declaration <: Statement { }

Any declaration node. Note that declarations are considered statements; this is because declarations can appear in any statement context.

FunctionDeclaration

interface FunctionDeclaration <: Function, Declaration {
    type: "FunctionDeclaration";
    id: Identifier;
}

A function declaration. Note that unlike in the parent interface Function, the id cannot be null.

VariableDeclaration

interface VariableDeclaration <: Declaration {
    type: "VariableDeclaration";
    declarations: [ VariableDeclarator ];
    kind: "var";
}

A variable declaration.

VariableDeclarator

interface VariableDeclarator <: Node {
    type: "VariableDeclarator";
    id: Pattern;
    init: Expression | null;
}

A variable declarator.

Expressions

interface Expression <: Node { }

Any expression node. Since the left-hand side of an assignment may be any expression in general, an expression can also be a pattern.

ThisExpression

interface ThisExpression <: Expression {
    type: "ThisExpression";
}

A this expression.

ArrayExpression

interface ArrayExpression <: Expression {
    type: "ArrayExpression";
    elements: [ Expression | null ];
}

An array expression.

ObjectExpression

interface ObjectExpression <: Expression {
    type: "ObjectExpression";
    properties: [ Property ];
}

An object expression.

Property

interface Property <: Node {
    type: "Property";
    key: Literal | Identifier;
    value: Expression;
    kind: "init" | "get" | "set";
}

A literal property in an object expression can have either a string or number as its value. Ordinary property initializers have a kind value "init"; getters and setters have the kind values "get" and "set", respectively.

FunctionExpression

interface FunctionExpression <: Function, Expression {
    type: "FunctionExpression";
}

A function expression.

Unary operations

UnaryExpression

interface UnaryExpression <: Expression {
    type: "UnaryExpression";
    operator: UnaryOperator;
    prefix: boolean;
    argument: Expression;
}

A unary operator expression.

UnaryOperator

enum UnaryOperator {
    "-" | "+" | "!" | "~" | "typeof" | "void" | "delete"
}

A unary operator token.

UpdateExpression

interface UpdateExpression <: Expression {
    type: "UpdateExpression";
    operator: UpdateOperator;
    argument: Expression;
    prefix: boolean;
}

An update (increment or decrement) operator expression.

UpdateOperator

enum UpdateOperator {
    "++" | "--"
}

An update (increment or decrement) operator token.

Binary operations

BinaryExpression

interface BinaryExpression <: Expression {
    type: "BinaryExpression";
    operator: BinaryOperator;
    left: Expression;
    right: Expression;
}

A binary operator expression.

BinaryOperator

enum BinaryOperator {
    "==" | "!=" | "===" | "!=="
         | "<" | "<=" | ">" | ">="
         | "<<" | ">>" | ">>>"
         | "+" | "-" | "*" | "/" | "%"
         | "|" | "^" | "&" | "in"
         | "instanceof"
}

A binary operator token.

AssignmentExpression

interface AssignmentExpression <: Expression {
    type: "AssignmentExpression";
    operator: AssignmentOperator;
    left: Pattern | Expression;
    right: Expression;
}

An assignment operator expression.

AssignmentOperator

enum AssignmentOperator {
    "=" | "+=" | "-=" | "*=" | "/=" | "%="
        | "<<=" | ">>=" | ">>>="
        | "|=" | "^=" | "&="
}

An assignment operator token.

LogicalExpression

interface LogicalExpression <: Expression {
    type: "LogicalExpression";
    operator: LogicalOperator;
    left: Expression;
    right: Expression;
}

A logical operator expression.

LogicalOperator

enum LogicalOperator {
    "||" | "&&"
}

A logical operator token.

MemberExpression

interface MemberExpression <: Expression, Pattern {
    type: "MemberExpression";
    object: Expression;
    property: Expression;
    computed: boolean;
}

A member expression. If computed is true, the node corresponds to a computed (a[b]) member expression and property is an Expression. If computed is false, the node corresponds to a static (a.b) member expression and property is an Identifier.

ConditionalExpression

interface ConditionalExpression <: Expression {
    type: "ConditionalExpression";
    test: Expression;
    alternate: Expression;
    consequent: Expression;
}

A conditional expression, i.e., a ternary ?/: expression.

CallExpression

interface CallExpression <: Expression {
    type: "CallExpression";
    callee: Expression;
    arguments: [ Expression ];
}

A function or method call expression.

NewExpression

interface NewExpression <: Expression {
    type: "NewExpression";
    callee: Expression;
    arguments: [ Expression ];
}

A new expression.

SequenceExpression

interface SequenceExpression <: Expression {
    type: "SequenceExpression";
    expressions: [ Expression ];
}

A sequence expression, i.e., a comma-separated sequence of expressions.

Patterns

Destructuring binding and assignment are not part of ES5, but all binding positions accept Pattern to allow for destructuring in ES6. Nevertheless, for ES5, the only Pattern subtype is Identifier.

interface Pattern <: Node { }

ES6 / ES2015 AST node types

Programs

extend interface Program {
    sourceType: "script" | "module";
    body: [ Statement | ModuleDeclaration ];
}

Parsers must specify sourceType as "module" if the source has been parsed as an ES6 module. Otherwise, sourceType must be "script".

Functions

extend interface Function {
    generator: boolean;
}

Statements

ForOfStatement

interface ForOfStatement <: ForInStatement {
    type: "ForOfStatement";
}

Declarations

VariableDeclaration

extend interface VariableDeclaration {
    kind: "var" | "let" | "const";
}

Expressions

interface Super <: Node {
    type: "Super";
}

extend interface CallExpression {
    callee: Expression | Super;
}

extend interface MemberExpression {
    object: Expression | Super;
}

A super pseudo-expression.

interface SpreadElement <: Node {
    type: "SpreadElement";
    argument: Expression;
}

extend interface ArrayExpression {
    elements: [ Expression | SpreadElement | null ];
}

extend interface CallExpression {
    arguments: [ Expression | SpreadElement ];
}

Spread expression, e.g., [head, ...iter, tail], f(head, ...iter, ...tail).

FIXME: This describes the Esprima and Acorn behaviors, which is not currently aligned with the SpiderMonkey behavior.

extend interface AssignmentExpression {
    left: Pattern;
}

Note that pre-ES6 code was allowed to pass references around and so left was much more liberal; an implementation might choose to continue using old definition if it needs to support such legacy code.

extend interface Property {
    key: Expression;
    method: boolean;
    shorthand: boolean;
    computed: boolean;
}

ArrowFunctionExpression

interface ArrowFunctionExpression <: Function, Expression {
    type: "ArrowFunctionExpression";
    body: FunctionBody | Expression;
    expression: boolean;
}

A fat arrow function expression, e.g., let foo = (bar) => { /* body */ }.

YieldExpression

interface YieldExpression <: Expression {
    type: "YieldExpression";
    argument: Expression | null;
    delegate: boolean;
}

A yield expression.

Template Literals

TemplateLiteral

interface TemplateLiteral <: Expression {
    type: "TemplateLiteral";
    quasis: [ TemplateElement ];
    expressions: [ Expression ];
}

TaggedTemplateExpression

interface TaggedTemplateExpression <: Expression {
    type: "TaggedTemplateExpression";
    tag: Expression;
    quasi: TemplateLiteral;
}

TemplateElement

interface TemplateElement <: Node {
    type: "TemplateElement";
    tail: boolean;
    value: {
        cooked: string;
        raw: string;
    };
}

Patterns

ObjectPattern

interface AssignmentProperty <: Property {
    type: "Property"; // inherited
    value: Pattern;
    kind: "init";
    method: false;
}

interface ObjectPattern <: Pattern {
    type: "ObjectPattern";
    properties: [ AssignmentProperty ];
}

ArrayPattern

interface ArrayPattern <: Pattern {
    type: "ArrayPattern";
    elements: [ Pattern | null ];
}

RestElement

interface RestElement <: Pattern {
    type: "RestElement";
    argument: Pattern;
}

AssignmentPattern

interface AssignmentPattern <: Pattern {
    type: "AssignmentPattern";
    left: Pattern;
    right: Expression;
}

Classes

interface Class <: Node {
    id: Identifier | null;
    superClass: Expression | null;
    body: ClassBody;
}

ClassBody

interface ClassBody <: Node {
    type: "ClassBody";
    body: [ MethodDefinition ];
}

MethodDefinition

interface MethodDefinition <: Node {
    type: "MethodDefinition";
    key: Expression;
    value: FunctionExpression;
    kind: "constructor" | "method" | "get" | "set";
    computed: boolean;
    static: boolean;
}

ClassDeclaration

interface ClassDeclaration <: Class, Declaration {
    type: "ClassDeclaration";
    id: Identifier;
}

ClassExpression

interface ClassExpression <: Class, Expression {
    type: "ClassExpression";
}

MetaProperty

interface MetaProperty <: Expression {
    type: "MetaProperty";
    meta: Identifier;
    property: Identifier;
}

Modules

ModuleDeclaration

interface ModuleDeclaration <: Node { }

A module import or export declaration.

ModuleSpecifier

interface ModuleSpecifier <: Node {
    local: Identifier;
}

A specifier in an import or export declaration.

Imports

ImportDeclaration

interface ImportDeclaration <: ModuleDeclaration {
    type: "ImportDeclaration";
    specifiers: [ ImportSpecifier | ImportDefaultSpecifier | ImportNamespaceSpecifier ];
    source: Literal;
}

An import declaration, e.g., import foo from "mod";.

ImportSpecifier

interface ImportSpecifier <: ModuleSpecifier {
    type: "ImportSpecifier";
    imported: Identifier;
}

An imported variable binding, e.g., {foo} in import {foo} from "mod" or {foo as bar} in import {foo as bar} from "mod". The imported field refers to the name of the export imported from the module. The local field refers to the binding imported into the local module scope. If it is a basic named import, such as in import {foo} from "mod", both imported and local are equivalent Identifier nodes; in this case an Identifier node representing foo. If it is an aliased import, such as in import {foo as bar} from "mod", the imported field is an Identifier node representing foo, and the local field is an Identifier node representing bar.

ImportDefaultSpecifier

interface ImportDefaultSpecifier <: ModuleSpecifier {
    type: "ImportDefaultSpecifier";
}

A default import specifier, e.g., foo in import foo from "mod.js".

ImportNamespaceSpecifier

interface ImportNamespaceSpecifier <: ModuleSpecifier {
    type: "ImportNamespaceSpecifier";
}

A namespace import specifier, e.g., * as foo in import * as foo from "mod.js".

Exports

ExportNamedDeclaration

interface ExportNamedDeclaration <: ModuleDeclaration {
    type: "ExportNamedDeclaration";
    declaration: Declaration | null;
    specifiers: [ ExportSpecifier ];
    source: Literal | null;
}

An export named declaration, e.g., export {foo, bar};, export {foo} from "mod"; or export var foo = 1;.

Note: Having declaration populated with non-empty specifiers or non-null source results in an invalid state.

ExportSpecifier

interface ExportSpecifier <: ModuleSpecifier {
    type: "ExportSpecifier";
    exported: Identifier;
}

An exported variable binding, e.g., {foo} in export {foo} or {bar as foo} in export {bar as foo}. The exported field refers to the name exported in the module. The local field refers to the binding into the local module scope. If it is a basic named export, such as in export {foo}, both exported and local are equivalent Identifier nodes; in this case an Identifier node representing foo. If it is an aliased export, such as in export {bar as foo}, the exported field is an Identifier node representing foo, and the local field is an Identifier node representing bar.

ExportDefaultDeclaration

interface ExportDefaultDeclaration <: ModuleDeclaration {
    type: "ExportDefaultDeclaration";
    declaration: Declaration | Expression;
}

An export default declaration, e.g., export default function () {}; or export default 1;.

ExportAllDeclaration

interface ExportAllDeclaration <: ModuleDeclaration {
    type: "ExportAllDeclaration";
    source: Literal;
}

An export batch declaration, e.g., export * from "mod";.

ES7 / ES2016 node types

BinaryOperator

extend enum BinaryOperator {
    "**"
}

AssignmentOperator

extend enum AssignmentOperator {
    "**="
}

ES8 / ES2017 AST node types

Function

extend interface Function {
    async: boolean;
}

AwaitExpression

interface AwaitExpression <: Expression {
    type: "AwaitExpression";
    argument: Expression;
}

ESTree AST Descriptor Syntax - gregswindle/eslint-plugin-crc GitHub Wiki

Table of contents

ES5 / ES2009 AST node types

Node objects

Identifier

Literal

RegExpLiteral

Programs

Functions

Statements

ExpressionStatement

Directive

BlockStatement

FunctionBody

EmptyStatement

DebuggerStatement

WithStatement

Control flow

ReturnStatement

LabeledStatement

BreakStatement

ContinueStatement

Choice

IfStatement

SwitchStatement

SwitchCase

Exceptions

ThrowStatement

TryStatement

CatchClause

Loops

WhileStatement

DoWhileStatement

ForStatement

ForInStatement

Declarations

FunctionDeclaration

VariableDeclaration

VariableDeclarator

Expressions

ThisExpression

ArrayExpression

ObjectExpression

Property

FunctionExpression

Unary operations

UnaryExpression

UnaryOperator

UpdateExpression

UpdateOperator

Binary operations

BinaryExpression

BinaryOperator

AssignmentExpression

AssignmentOperator

LogicalExpression

LogicalOperator

MemberExpression

ConditionalExpression

CallExpression

NewExpression

SequenceExpression

Patterns

ES6 / ES2015 AST node types

Programs

Functions

Statements

ForOfStatement

Declarations

VariableDeclaration

Expressions

ArrowFunctionExpression

YieldExpression

Template Literals

TemplateLiteral

TaggedTemplateExpression

TemplateElement

Patterns

ObjectPattern

ArrayPattern

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